1. Field of the Invention
The present invention relates to flail chain unloaders for discharging particulate material from the lower outlet of an upright storage vessel and, more particularly, to an unloader of the character described which is suitable for use with relatively fine or small sized particulate type of materials stored in an upwardly extending storage vessel and which materials are free-flowing and do not tend to bridge, form open pockets or a void in the region around the unloader while the unloader is in a stationary or inoperative condition.
2. Description of the Prior Art
Flail chain type unloaders have long been used for discharging silage material from upright agricultural silos and these type of unloaders employ swinging flail chains attached to an upright, centrally located, rotating shaft at succeeding spaced apart levels with ever increasing chain lengths until reaching a maximum length chain having an outer end movable in a path closely adjacent an inside wall surface of the silo. Additional upper flail chains of shorter length may normally be provided and spaced above the maximum length chains in order to dig out a crown-shaped bridge or roof of an open space in the silage mass at the bottom of the silo around the unloader. The silage bridge above the unloader permits the silage to move slowly downwardly into the path of the flail chains during an unloading operation. When the unloader is shut down, the silage normally tends to remain in a bridged condition providing a somewhat open pocket or void around the unloader so that when the unloader is again started by rotation of the shaft, the flail chains of varying lengths can move upwardly after becoming disentangled from one another and out of the hanging or rest position to occupy a normal operating horizontal position wherein the chains eat away or cut away a bottom layer of the silage bridging across the silo so that the entire mass of silage above the unloader moves slowly down as the unloading operation proceeds.
Typical prior art flail chain unloaders for silage in agricultural silos are disclosed in U.S. Pat. Nos. 3,907,131; 3,142,656 and 4,079,848, which patents are assigned to the same assignee as the present application, and which patents are incorporated herein by reference. These type of silage unloaders may be unsuitable for use with relatively fine and/or free-flowing particulate materials such as agricultural grains, wood chips, plastic beads, meat meal, fish meal, etc., which commodities are oftentimes stored in upright silos or vessels for commercial operations. In general, freely flowable materials stored in commercial and industrial silos such as sand and granular materials tend to flow more easily than stringly silage material and these free-flowing particulates tend to fill up a lower portion of the vessel surrounding the flail chain type unloader when stopped so that thereafter, upon initial start up of the unloader for the purpose of discharging material from the storage vessel, the elongated flail chains and particularly the longer ones at the upper levels, are often unable to become disentangled from the progressively shorter chains therebelow and ineffective discharge results. Sometimes the longer chains never become disentangled enough to move outwardly into the normal horizontally extending operating position for digging out and dislodging the material to flow downwardly into the discharge opening.
Attempts at using conventional types silage unloaders having chain lengths as illustrated in the foregoing patents for free-flowing particulates have sometimes been unsuccessful because of the inability of the upper, longer unloader chains to become disentangled from lower chains during initial start up.